Thursday, January 4, 2024

Coronal mass ejection from colossal New Year's Eve solar flare will strike Earth today

Space.com:

The coronal mass ejection CME was hurled into space by an X-class solar flare that burst from the surface of the sun at 4:55 p.m. EST (2155 GMT) on Sunday (Dec. 31). It is the most powerful flare that has happened on the sun during the current solar cycle, solar cycle 25, which began in Dec. 2019. In fact, the flare that ended 2023 with a bang is the largest that has been observed since Sept. 10, 2017, according to the Space Weather Prediction Center of the National Oceanic And Atmospheric Administration (NOAA).

I'm always amused by these comparisons articles like to make. "Largest that has been observed since 2017". We're approaching solar maximum so the flares will be the largest in the cycle. The solar cycle is ~11 years so the last maximum was in the early 2010s, and the last minimum was in the late 2010s. "This solar flare at near maximum was bigger than the ones at the minimum" has substantially less punch.

Storms like this have the capability to cause weak fluctuations in power grids and could have minor impacts on satellite operations. In addition to this, G1 geomagnetic storms can give rise to striking auroras, beautiful light shows seen over Earth, usually at higher latitudes.

In 2003, during the last solar maximum — the peak of the sun's activity during the solar cycle 24  — an X45 flare was seen erupting from the sun, the most powerful solar flare ever measured. 

A powerful X-class flare like the one seen on New Year's Eve has the potential for long-lasting radiation storms, which can damage satellites, including GPS, and affect aircraft flying near the poles of Earth, even giving passengers on these flights small radiation doses. X flares also have the potential to cause worldwide blackouts, if conditions were just right.

The Hill:

In an update Sunday evening, NOAA’s Space Weather Prediction Center (SWPC) released an image of the flare, which appeared as a large, glowing spot on the sun. You can see that image below. 


Image reproduced from thehill.com. Original caption: An X5 solar flare detected by NOAA’s Space Weather Prediction Center on December 31, 2023. (NOAA SWPC; cropped)

At an X5, Sunday’s flare was much smaller than the flare recorded in 2003. It was, however, the strongest since September 2017, when an X8.2 flare was detected, according to the SWPC. This flare also supersedes an X2.8 solar flare reported in the same region of the sun on December 14. At the time, the SWPC reported that flare was “likely one of the largest solar radio events ever recorded.”

Possible effects:

The SWPC said those using high-frequency radio signals (like emergency managers) may notice a “temporary degradation or complete loss of signal on much of the sunlit side of Earth” as a result of Sunday’s solar flare.


Previously on this blog:

 

Wednesday, January 3, 2024

New ultra-short period binary discovered

arXiv:

Binary evolution theory predicts that the second common envelope (CE) ejection can produce low-mass (0.32-0.36 Msun) subdwarf B (sdB) stars inside ultrashort-orbital-period binary systems, as their helium cores are ignited under nondegenerate conditions.

Here we report the discovery of a 20.5-minute-orbital-period ellipsoidal binary, TMTS J052610.43+593445.1, in which the visible star is being tidally deformed by an invisible carbon-oxygen white dwarf (WD) companion. 

phys.org:

The orbital periods of such detached sdB binary systems can be as short as 20 minutes. However, to date only four binaries of this type with orbital periods below one hour have been found.

Now, a team of astronomers led by Jie Lin of the Tsinghua University in Beijing, China, reports the detection of a new sdB binary with an extremely short orbital period...they discovered a dozen such objects, and one of them, which received designation TMTS J052610.43+593445.1 (or J0526 for short) turned out to be an sdB binary with an orbital period of approximately 20.5 minutes.

BNN Breaking:

The white dwarf, although ten times smaller than the sun, has a mass of 0.735 solar masses and an effective temperature of 25,400 K. This binary system presents astronomers with a unique opportunity to study the physics and evolution of stars under extreme conditions.

In about 1.5 million years, the subdwarf will begin transferring mass to the white dwarf at an even shorter orbital period, leading to the formation of an AM CVn star through the helium-star channel. This process is pivotal for understanding binary evolution from the second common envelope ejection to the formation of AM CVn stars. The discovery of TMTS J052610.43+593445.1 could play a significant role in investigating these binary evolution paths.

  

Previously on this blog:

Tuesday, January 2, 2024

JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like

arXiv:

In this letter, we used James Webb Space Telescope (JWST) images from the Cosmic Evolution Early Release Science Survey to visually identify spiral galaxies with redshift 0.5≤z≤4 and stellar mass ≥1010M⊙. Out of 873 galaxies, 216 were found to have a spiral structure.

These fractions are higher than the fractions observed with the Hubble Space Telescope (HST). We even detect possible spiral-like features at redshifts z>3.

This fraction is surprisingly high and implies that the formation of spiral arms, as well as disks, was earlier in the universe. 

Phys.org:

Of these galaxies, 216 were classified as spirals. The authors were careful to note that some may be merging galaxies that were misclassified, but even then 108 of the galaxies were unanimously classified as spirals by evaluators. When the team arranged them by redshift, they found that while the fraction of spirals decreased as you went further into the past, the fraction of spirals at redshifts above z = 3 was much higher than expected. When the team calibrated observations, they found about a fifth of galaxies at z = 3 are spiral galaxies. These very early galaxies would have had to become spirals less than two billion years after the Big Bang, meaning that there would have been little time for mergers and collisions to be the cause.

If spiral galaxies were more common in the early universe than expected, it could indicate that certain conditions or mechanisms favored the formation of spiral structures at that time. This is quite at odds with the current understanding of what structures were favored during these early epochs of the Universe's development.


Previously on this blog:

How many planets could be in the Kuiper Belt?

ApJL

Motivated by recent measurements of the free-floating-planet mass function at terrestrial masses, we consider the possibility that the solar system may have captured a terrestrial planet early in its history. We show that ∼1.2 captured free-floating planets with mass strictly greater than that of Mars may exist in the outer solar system, with a median predicted distance of ∼1400 au.

To evaluate the expected mass of the most massive captured free-floating planet as a function of the maximum semimajor axis, given the arguments presented in Section 2, we implement a Monte Carlo simulation.

This is an interesting calculation, but the result of ~1 free-floating planet does not have a reported error and seems extremely sensitive to the mass function. Equation 1 gives the mass function of free-forming planets:

The coefficient on the power-law term has substantial errorbars, changing the result of the mass function by up to 75% if alpha ~ 1. Examining alpha as well, the paper reports that alpha ~ 0.96 \pm 0.47, which would have a substantial effect on the value of the mass function. It wasn't immediately clear how this substantial variation affected the number of planets detected. Figure 1 shows the confidence intervals on the mass estimate for a planet of abundance unity, but I wasn't able to immediately grasp how to convert this into an errorbar on the planet abundance estimate. Then Figure 2 shows the cumulative fraction and expected number of captured free-floating planets, but doesn't show the confidence intervals. So overall, it's hard to assess the free-floating planet abundance estimate from their simulations given the huge spread on the parameters. The estimate changes from ~1 to ~3 with a change of binning, which is expected but also highlights how uncertain the estimate and approach are, so it would been interesting to see a more thorough exploration of this.

Phys.org:

A recent study published in the Astrophysical Journal Letters investigates the potential existence of Mars-sized free-floating planets (FFPs)—also known as rogue planets, starless planets, and wandering planets—that could have been captured by our sun's gravity long ago and orbit in the outer solar system approximately 1,400 astronomical units (AU) from the sun.

Scientists currently hypothesize that rogue planets are formed from two scenarios: As part of their own solar system but are then somehow ejected into the cosmos, or they form in isolation. But what is the significance of studying free-floating planets, overall?

After conducting approximately 100,000,000 simulations, the results indicate the potential for the existence of a Mars-sized, or even a Mercury-sized planetary body somewhere in the outer solar system approximately 1,400 AU from the Sun.

Universe Today:

Siraj recommends in his study that future work could include gaining greater understanding of how rogue planets are captured in the first place, along with investigating observational tests to identify where to look in the sky for rogue planets, as well. He also notes how microlensing has become the preferred method in identifying rogue planets based on past studies.

Rogue planet capture is extremely interesting for sure. I'm also super interested in the related phenomenon of JuMBOs (Jupiter-Mass Binary Objects), which are forcing astrophysicists to confront the same tough questions as this study.


Previously on this blog:

Tuesday, December 5, 2023

Saturn's icy moon may hold the building blocks of life

Phys.org:

Evidence indicates that Saturn's icy moon Enceladus is an 'ocean world' that contains all three, making it a prime target in the search for life. 

During its 20-year mission, NASA's Cassini spacecraft discovered that ice plumes spew from Enceladus' surface at approximately 800 miles per hour (400 m/s). These plumes provide an excellent opportunity to collect samples and study the composition of Enceladus' oceans and their potential habitability.

Now, researchers from the University of California San Diego have shown unambiguous laboratory evidence that amino acids transported in these ice plumes can survive impact speeds of up to 4.2 km/s, supporting their detection during sampling by spacecraft.  

PNAS:

The icy moons of Saturn and Jupiter, Enceladus and Europa, are particularly promising for hosting life, as they have shown evidence for the three important criteria: water, energy, and organic chemicals. Both moons eject their subsurface ocean material as a plume of icy particles, providing the opportunity to study the ocean composition and potential habitability via plume flythrough sampling. 

We show that amino acids entrained in ice grains can be detected intact after impact at speeds up to 4.2 km/s and that salt reduces their detectability, validating the predictions from other model systems. Our results provide a benchmark for this orbital sampling method to successfully detect signs of life and for the interpretation of past and future data.


I've always been personally excited by the original Enceladus discovery made by Cassini. It was already such a bizarre little moon to begin with, with the smooth southern geography, but the discovery of these liquid water plumes indicating a warm ocean under the surface was absolutely wonderful. There tends to be excitement and interest in finding aliens far outside of Earth, but if we honest-to-goodness to find alien life or at least the building blocks for it, it'll likely be in the plumes of Enceladus, quite close to home.


Monday, November 20, 2023

Detection of long-lasting aurora-like radio emission above a sunspot

nature astronomy:

Here we report observations of long-lasting solar radio bursts with high brightness temperature, wide bandwidth and high circular polarization fraction akin to these auroral and exo-auroral radio emissions, albeit two to three orders of magnitude weaker than those on certain low-mass stars. Spatially, spectrally and temporally resolved analysis suggests that the source is located above a sunspot where a strong, converging magnetic field is present. 

Our findings offer new insights into the origin of such intense solar radio bursts and may provide an alternative explanation for aurora-like radio emissions on other flare stars with large starspots.


(Figure 1 caption) a, Example of a VLA snapshot image at 1.0 GHz (orange) of the radio emission from the sunspot with the image of the radio-hosting NOAA 12529 AR observed in EUV wavelengths by the AIA, 171 Å (blue), 94 Å (cyan) and 1,600 Å (red) overlaid on the photospheric image observed by the HMI aboard the SDO. Also shown is a VLA 3.8 GHz image (magenta) of the radio emission from the flare site. b, Closer view of the sunspot region (box in a). The 1.0 GHz and 3.8 GHz are shown as yellow and magenta contours, respectively, at 50%, 70% and 90% of the maximum. The white box in b is discussed further at Fig. 4.

LiveScience:

Scientists have spotted a stunning "aurora-like" display of crackling radio waves over the surface of the sun that is strikingly similar to the Northern Lights on Earth. 

"This is quite unlike the typical, transient solar radio bursts typically lasting minutes or hours," lead author Sijie Yu, an astronomer at New Jersey Institute of Technology's Center for Solar-Terrestrial Research (NJIT-CSTR), said in a statement. "It's an exciting discovery that has the potential to alter our comprehension of stellar magnetic processes."

The researchers say their discovery has opened up new ways to study the sun's activity, and they have begun poring through archival data to find hidden evidence of past solar auroras. "We're beginning to piece together the puzzle of how energetic particles and magnetic fields interact in a system with the presence of long-lasting starspots," study co-author Surajit Mondal, a solar physicist at NJIT, said in the statement. "Not just on our own Sun but also on stars far beyond our solar system."

This is a really exciting discovery! The resolution required to do this kind of work is fairly low so it seems completely plausible that past observations of the Sun in radio may have captured these sorts of effects. The duration is also interesting--a week is a long time for solar processes. Something I'm particularly curious about is whether we expect to see more of these now that a long and early solar maximum is just around the corner.

NOAA:

NOAA’s Space Weather Prediction Center (SWPC) issued a revised prediction for solar activity during Solar Cycle 25 that concludes solar activity will increase more quickly and peak at a higher level than that predicted by an expert panel in December 2019. The updated prediction now calls for Solar Cycle 25 to peak between January and October of 2024, with a maximum sunspot number between 137 and 173.

The solar maximum is a period in the solar cycle when the Sun's activity, particularly in terms of sunspots and solar flares, is at its highest. The solar cycle is an approximately 11-year cycle during which the Sun undergoes a regular pattern of changes in solar activity. This cycle is characterized by the waxing and waning of the number of sunspots on the Sun's surface.

During solar maximum, the number of sunspots is at its peak, and solar activity is generally more intense. Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are associated with strong magnetic activity and are often the source of solar flares and coronal mass ejections (CMEs). It therefore seems pretty reasonable to me that we might expect more of these aurora-like transients, which seemed to form above a large sunspot.


Previously on this blog:

ALMA Achieve Unprecedented Resolution to Observe the Universe

ALMA Observatory:

An international team of astronomers and engineers has successfully conducted an observation that achieved an extraordinary resolution of 5 milliarcseconds, using ALMA's highest frequency Band 10 receiver and an array configuration that spans 16 kilometers. 

This groundbreaking observation allowed the team to capture unprecedented details of a maser around an evolved star within the Milky Way. 

Yoshiharu Asaki, the ALMA Astronomer who led this project, highlighted the collaborative effort: "This remarkable achievement in high-resolution imaging through ALMA's advanced capabilities marks a significant milestone in our quest to understand the Universe. The success of the Band 10 high-resolution observation showcases our commitment to innovation and reinforces ALMA's position as a leader in astronomical discovery. We are excited about the new possibilities for the scientific community."

5 milliarcseconds is certainly an impressive resolution. For comparison, the VLBI array that examined SN 1993J at 8 GHz achieved a resolution of ~1 milliarcsecond. For a single station to achieve this is incredible.

ApJ:

The Atacama Large Millimeter/submillimeter Array (ALMA) was used in 2021 to image the carbon-rich evolved star R Lep in Bands 8–10 (397–908 GHz) with baselines up to 16 km. The goal was to validate the calibration...and the imaging procedures required to obtain the maximum angular resolution achievable with ALMA.

It's quite interesting seeing that the paper is very focused on what amounts to a test and validation of the capabilities of ALMA, but still got good coverage in the media. This isn't a bad thing at all--usually buzzwordy science results grab all the attention--and it's nice to see a shift towards interest in some of the technical aspects of the field.

 

Coronal mass ejection from colossal New Year's Eve solar flare will strike Earth today

Space.com : The coronal mass ejection CME was hurled into space by an X-class solar flare that burst from the surface of the sun at 4:55 p.m...