A crescent moon over Manhattan (New York City, 1946).
A crescent moon over Manhattan (New York City, 1946).
Will you come with me
to reside in a new planet—
where the atmosphere’s bleak
under its stellar morse code.
A world for me and you
Split the sky in half
Just the two of us
got a new journal for uni as my current one wouldn’t even last for first term. what are the spreads you use most? (e.g. mood tracker, sleep, books…) looking for some inspiration
Arp 78: Peculiar Galaxy in Aries
(xxxedit and linkxxx) Peculiar spiral galaxy Arp 78 is found within the boundaries of the head strong constellation Aries, some 100 million light-years beyond the stars and nebulae of our Milky Way galaxy. Also known as NGC 772, the island universe is over 100,000 light-years across and sports a single prominent outer spiral arm in this detailed cosmic portrait. Its brightest companion galaxy, compact NGC 770, is toward the upper right of the larger spiral. NGC 770’s fuzzy, elliptical appearance contrasts nicely with a spiky foreground Milky Way star in matching yellowish hues. Tracking along sweeping dust lanes and lined with young blue star clusters, Arp 78’s large spiral arm is likely due to gravitational tidal interactions. Faint streams of material seem to connect Arp 78 with its nearby companion galaxies.
Image Copyright: Bernard Miller
Galaxies, Nebulas, and Supernova Remnants
First Methodist Episcopal Church (now known as First United Methodist Church) is a historic church in Massillon, Ohio, United States, located at 301 Lincoln Way East. It is of stone and sandstone construction with a copper roof in the Richardsonian Romanesque style. The building was dedicated in June 1895 and was added to the U.S. National Register of Historic Places on August 22, 1985.
Another SpaceTime from the archives….
Forecasting Eruptions of Solar Flares
By Susanna Kohler
Can we tell when a solar flare will lead to a potentially hazardous eruption of plasma from the Sun?
A new look at hundreds of past solar flares may provide some clues.
Belches from the Sun
Two of the most energetic phenomena in our solar system are solar flares and coronal mass ejections (CMEs).
While both are explosions produced in active regions on the Sun, they are distinctly different: solar flares are intense bursts of radiation spanning the electromagnetic spectrum, whereas CMEs are violent, directed eruptions of hot, magnetized plasma — sometimes containing more than a billion tons of matter — into space.
While the two phenomena sometimes arise hand in hand, this is not always the case.
The Earth’s magnetic field does a good job of protecting us from the greatest impact of these eruptions, but a CME directed at Earth still has the potential to be hazardous to our technology and communications systems, as well as to any unshielded life (such as astronauts on a lunar mission).
Scientists are therefore interested in better understanding which solar flares are likely to be eruptive — i.e., accompanied by a CME — and which ones will instead be confined.
A Decade of Activity
To this end, a team of scientists led by Ting Li (Chinese Academy of Sciences) recently constructed an extensive catalog of large (M- and X-class) solar flares and associated CMEs observed in 2010–2019 — a time period that spans nearly the entirety of the Sun’s most recent solar activity cycle.
The team then analyzed the 322 resulting flares and cataloged them as either eruptive or confined, depending on whether or not there was an associated CME.
Finally, Li and collaborators analyzed the properties of the active regions from which the flares and CMEs arose.
Exercising Magnetic Restraint
Li and collaborators found an anticorrelation between the total magnetic flux of active regions and the proportion of eruptive flares.
That means that the active regions with especially small magnetic fluxes were very likely to have flares with accompanying CMEs, whereas the active regions with especially large magnetic fluxes were more likely to have confined flares with no eruptions.
Why? Perhaps counterintuitively, the stronger magnetic flux actually helps to hold back the flares, preventing them from breaking out and expelling matter in a CME.
The authors find additional evidence supporting this picture: the critical decay index height — a measure of how quickly the magnetic field drops off with height — indicates that the active regions with greater flux also have stronger confinement.
Space Weather Predictions
Li and collaborators’ publicly available catalog and results provide us with valuable clues to help forecast CMEs in association with large flares.
In addition, these outcomes could have implications beyond our own solar system: they may help us to better understand the flares we’ve witnessed from other stars and even assess the potential habitability of their planets.
As we learn more, future solar and stellar belches may become just a little less unpredictable.
“Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares,” Ting Li et al 2020 ApJ 900 128. doi:10.3847/1538-4357/aba6ef
TOP IMAGE….In a coronal mass ejection, solar material erupts into space in a violent outburst of hot, magnetized plasma. [NASA Goddard SFC]
CENTRE IMAGE….A large solar flare may or may not be accompanied by a violent ejection of matter in a CME. [NASA/SDO]
LOWER IMAGE….Top: For active regions with low magnetic flux, more flares tend to be eruptive (blue), whereas for active regions with high magnetic flux, more flares tend to be confined (red). Bottom: The proportion of eruptive flares (PE) decreases with increasing active region magnetic flux. [Adapted from Li et al. 2020]
BOTTOM IMAGE….The critical decay index height vs. active region magnetic flux for eruptive (blue) and confined (red) flares shows that regions with more magnetic flux are also more confined. [Adapted from Li et al. 2020]
Different Views of a Fast Radio Burst
By Tarini Konchady
Fast radio bursts are perplexing astrophysical phenomena.
As their name suggests, they’re essentially short radio signals, but they pack a surprising amount of energy.
More unusual is that some fast radio bursts repeat, while others are one-off events.
Repeating fast radio bursts present an opportunity to study bursts in more detail.
So what do we see when we observe a burst at multiple frequencies simultaneously?
A Tendency to Repeat Itself
Fast radio bursts (FRBs) typically last only a few milliseconds, but the strength with which they’re detected suggests that FRBs are produced by extremely energetic processes.
What these processes are is an open question.
Practically all known FRBs originated outside the Milky Way, though that might no longer be the case.
Some FRBs are known to repeat, allowing for their origin to be pinpointed far more accurately than one-off FRBs.
The first known repeating FRB, called FRB 121102, lives in a dwarf galaxy over 2 billion light-years away.
FRB 121102 has produced hundreds of bursts since its discovery, and studies have determined that it can be detected at multiple radio frequencies.
A new study led by Walid Majid (Jet Propulsion Laboratory/California Institute of Technology) revisited FRB 121102 using DSS-43, a 70-meter radio telescope in NASA’s Deep Space Network.
The goal of this study was to probe FRB 121102’s bursts at higher frequencies than previously studied and to examine the bursts’ appearance in broadband observations.
Only One Right Frequency?
Broadband observations of FRBs provide spectra of the bursts, and spectra are extremely useful.
In the case of FRBs, spectral features could either be caused by the mechanism of the burst itself, or they could instead have been added as the signal propagated through the host environment, across intergalactic space, and then through the Milky Way to reach us.
Majid and collaborators observed FRB 121102 with DSS-43 for nearly six hours on September 19, 2019.
The observations were centered at 2.25 (S band) and 8.36 gigahertz (X band) with usable bandwidths of ~100 and ~430 megahertz respectively.
Six bursts were observed in this time — but they were only seen in the lower-frequency S band!
It All Depends on How You Look at It
The lack of a high-frequency detection for FRB 121102 is interesting, especially since the X band had a larger bandwidth than the S band.
Does this frequency dependence provide insight into the FRB emission mechanism? Or does it only arise as the signal propagates to us?
Majid and collaborators explored the possibility that scintillation in our galaxy could be responsible for the lack of visible activity in the X band.
In the context of FRBs, galactic scintillation is the observation of multiple bursts at various frequencies, caused by burst photons interacting with material in the Milky Way.
The authors show that galactic scintillation can’t account for FRB 121102’s observations, suggesting the frequency dependence may have more to do with intrinsic properties of the emission mechanism or properties of the FRB’s host galaxy.
As with most things in astronomy, more observations are required. Wajid and collaborators concluded that dense, multi-frequency observations of FRB 121102 would go a long way to understanding its behavior.
And so the mystery of FRBs continues!
“A Dual-band Radio Observation of FRB 121102 with the Deep Space Network and the Detection of Multiple Bursts,” Walid A. Majid et al 2020 ApJL 897 L4. doi:10.3847/2041-8213/ab9a4a
TOP IMAGE….Artist’s conception of the localization of a fast radio burst to its host galaxy. [Danielle Futselaar]
CENTRE IMAGE….FRB 121102, the first fast radio burst found to repeat, was also the first to be localized in the sky. [Gemini Observatory/AURA/NSF/NRC]
LOWER IMAGE….The radio telescope DSS-43, which is located in Canberra, Australia. [NASA]
BOTTOM IMAGE….The brightest burst observed from FRB 121102 as seen in the S band (bottom panel) and not seen in the X band (middle panel). The top panel shows the strength of the burst signal in the S band (black line) and the X band (grey line) as the signal-to-noise ratio versus time. In the middle and bottom panels, the signal is shown as frequency versus time, with dark areas corresponding to the burst. The time unit is milliseconds. [Adapted from Majid et al. 2020]
N11, Star Clouds
Breaking Distant Light via NASA