from the world's big
A gigantic star makes off during an eight-year gap in observations.
- The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
- It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
- Maybe it's still there, but much less luminous and/or covered by dust.
A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?
The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.
Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.
In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.
Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."
The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.
In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.
Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."
Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.
Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."
Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."
A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.
LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.
Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."
The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:
"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."
Can this end flat-Earth theory once and for all?
- Despite centuries of evidence proving otherwise, there are an alarming number of people around the world who genuinely believe that the earth is flat. Bill Nye The Science Guy, NASA astronomer Michelle Thaller, and Neil deGrasse Tyson strongly disagree.
- From simple experiments like standing at a seashore or looking through a telescope at other planets, to reading about navigation or viewing photos of Earth taken from space, the scientists share several ways that flat Earthers can see the truth for themselves.
- Tyson explains why this trend doesn't qualify as a scientific debate and why it is actually dangerous for people to believe and, even worse, pass on these objectively false ideas.
On other planets, blue skies and red sunsets aren't the norm.
- A NASA scientist created animated simulations of how sunsets likely appear on Mars, Venus, Uranus, and Titan, Saturn's largest moon.
- Sunsets appear differently on other planets because of differences in the atmosphere, which scatters light in unique ways.
- Studying alien atmospheres helps scientists better understand atmospheric processes on Earth, and helps narrow the search for habitable planets.
An illustration of Rayleigh scattering.
Scientificprotocols via YouTube<p>The result is a red sunset, produced by an optical phenomenon called <a href="https://en.wikipedia.org/wiki/Rayleigh_scattering" target="_blank">Rayleigh scattering</a>.</p>
A sunset on Mars. Taken by the Viking 2 Lander on June 14, 1978, this was the first photo of an alien sunset.
NASA<p><a href="https://science.gsfc.nasa.gov/sed/bio/geronimo.l.villanueva" target="_blank">Villanueva</a>'s simulations are now featured on NASA's <a href="https://psg.gsfc.nasa.gov/about.php" target="_blank">Planetary Spectrum Generator</a>, an online tool for studying the atmospheres and surfaces of distant planets. Studying alien atmospheres not only helps scientists better understand atmospheric processes on Earth, but also gives them a clearer idea of which planets may be habitable — or harbor life already.</p>
Researchers create a device to test a 50-year-old physics theory from the famed Roger Penrose.
- Scientists prove a 50-year-old physics theory by Roger Penrose.
- The theory explains how energy could be harvested from black holes by advanced aliens.
- Researchers from the University of Glasgow twisted sound waves to show that the effect Penrose described is real.
Check out how the researchers explain their work<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="18cab22ba8605e6eaba8784df05eeb1d"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/ES2VxhRAkUM?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
The set-up of the experiment.
Credit: University of Glasgow
It could be the most spectacular annular eclipse of the decade.
- An annular eclipse is a type of solar eclipse where the edge of the Sun remains visible around the Moon.
- The June 21 annular eclipse will occur when the Moon is nearly at its apogee, the point in the lunar orbit when the Moon is farthest away from Earth.
- Only some countries will be able to see the eclipse in person, but several organizations plan to livestream the event.
timeanddate.com<p>The annular eclipse may also provide views of the Sun's chromosphere — a pinkish layer of burning hydrogen — and "<a href="https://en.wikipedia.org/wiki/Baily%27s_beads" target="_blank">Baily's beads</a>," a visual effect of solar eclipses where streams of sunlight travel across the moon's rugged topography. The eclipse will begin at 12:47 a.m. ET and will last several hours, but each specific location on Earth will only be able to see it, weather permitting, for about one minute. </p>