About 97% of all stars in our Universe are destined to end their lives as white dwarf stars, which represents the final stage in their evolution. Like neutron stars, white dwarfs form after stars have exhausted their nuclear fuel and undergo gravitational collapse, shedding their outer layers to become super-compact stellar remnants. This will be the fate of our Sun billions of years from now, which will swell up to become a red giant before losing its outer layers.
Unlike neutron stars, which result from more massive stars, white dwarfs were once about eight times the mass of our Sun or lighter. For scientists, the density and gravitational force of these objects is an opportunity to study the laws of physics under some of the most extreme conditions imaginable. According to new research led by researchers from Caltech, one such object has been found that is both the smallest and most massive white dwarf ever seen.
The study that describes the research team’s findings appeared in the July 1st issue of the scientific journal Nature. The research was led by Ilaria Caiazzo, the Sherman Fairchild Postdoctoral Scholar Research Associate in Theoretical Astrophysics at Caltech, and included colleagues from Caltech, the University of British Columbia (UBC), UC Santa Cruz, and the Weizmann Institute of Science in Rehovot, Israel.
Artist’s impression of white dwarf ZTF J1901+1458 above the Moon in this artistic representation; in reality, the white dwarf lies 130 light-years away in the constellation of Aquila. Credit: Giuseppe Parisi
This white dwarf, known as ZTF J190132.9+145808.7 (aka. ZTF J1901+1458), is located about 130 light-years from Earth and is estimated to be 1.35 times as massive as our Sun. However, this white dwarf has a stellar radius of about 1810 km (1,125 mi) – slightly larger than the Moon (1,737.4 km; 1,080 mi) – which makes it the smallest and most massive white dwarf ever observed. As Caiazzo explained in a recent press statement from the W.M Keck Observatory:
“It may seem counterintuitive, but smaller white dwarfs happen to be more massive. This is due to the fact that white dwarfs lack the nuclear burning that keep up normal stars against their own self gravity, and their size is instead regulated by quantum mechanics.”
This white dwarf also has an extreme magnetic field, ranging from 600 to 900 MegaGauss (MG) over its entire surface, or roughly 1 billion times stronger than our Sun’s. This magnetic field has one of the fastest rotational periods ever observed in an isolated white dwarf, whipping around the star’s axis once every 6.94 minutes. What’s more, the study of this white dwarf is already offering astronomers insight into how binary systems end their lives.
This curious white dwarf was originally discovered by Kevin Burdge, a postdoctoral scholar at Caltech and a co-author of the recent study. Based on all-sky images taken by the Zwicky Transient Facility (ZTF) at Caltech’s Palomar Observatory, combined with data obtained by the ESA’s Gaia Observatory, it became clear that the white dwarf was also very massive and had a rapid rotation.
Artist’s rendition of a white dwarf from the surface of an orbiting exoplanet. Image Credit: Madden/Cornell University
Further characterizations were made using the 200-inch Hale Telescope at Palomar, the W. M. Keck Observatory, the Panoramic Survey Telescope and Rapid Response System (PanSTARRS), the ESA’s Gaia Observatory, and NASA’s Neil Gehrels Swift Observatory. Whereas spectra obtained by Keck’s Low-Resolution Imaging Spectrometer (LRIS)
Europa Clipper Could Help Discover if Jupiter’s Moon is Habitable
Since 1979, when the Voyager probes flew past Jupiter and its system of moons, scientists have speculated about the possibility of life within Europa. Based on planetary modeling, Europa is believed to be differentiated between a rocky and metallic core, an icy crust and mantle, and a warm water ocean up to 100 km (62 mi) in depth. Scientists theorize that this ocean is maintained by tidal flexing, where interaction with Jupiter’s powerful gravitational field leads to geological activity in Europa’s core and hydrothermal vents at the core-mantle boundary.
Investigating the potential habitability of Europa is the main purpose of NASA’s Europa Clipper mission, which will launch on October 10th, 2024, and arrive around Jupiter in April 2030. However, this presents a challenge for astrobiologists since the habitability of Europa is dependent on many interrelated parameters that require collaborative investigation. In a recent paper, a team of NASA-led researchers reviewed the objectives of the Europa Clipper mission and anticipated what it could reveal regarding the moon’s interior, composition, and geology.
The team consisted of researchers from the Johns Hopkins University Applied Physics Laboratory (JHUAPL), the Beyond Center at Arizona State University, the Woods Hole Oceanographic Institution (WHOI), Honeybee Robotics, the Southwest Research Institute (SwRI), the Planetary Science Institute (PSI), the Lunar and Planetary Laboratory (LPL), NASA’s Goddard Space Flight Center (GSFC) and Jet Propulsion Laboratory (JPL), and multiple universities. Their paper, “Investigating Europa’s Habitability with the Europa Clipper,” recently appeared in Space Science Reviews.
Could shallow lakes be locked away in Europa’s crust? Europa Clipper will find out. Credit: NASA
What is “Habitability”?
When it comes to the search for life beyond Earth (aka. astrobiology), all of humanity’s efforts are currently focused on Mars. This will change in the coming years as missions destined for the outer Solar System conduct detailed studies of “Ocean Worlds” – icy bodies with interior oceans. This includes Europa, Ganymede, Titan, Enceladus, Triton, and possibly Pluto and Charon. The Europa Clipper will be the first of these missions to arrive – followed by the ESA’s JUpiter ICy moons Explorer (JUICE) in 2031. It will spend the next four years orbiting Jupiter and making close flybys of Europa, studying its surface and interior with its advanced suite of instruments. As the Europa Study Team summarized in their 2012 report:
“Jupiter’s moon Europa is one the most promising candidates for hosting life today among ocean worlds in the Solar System. In its investigation of Europa’s habitability, the Europa Clipper mission seeks to understand the provenance of water, essential chemical elements and compounds, and energy, and how they might combine to make this moon’s environments suitable to support life.”
As the NASA-led team indicated in their study, the purpose of the Europa Clipper mission is not to detect life itself but to assess Europa’s ability to support life as we know it. This will consist of confirming (or refuting) the existence of Europa’s interior ocean and determining if it possesses the necessary chemical and energy sources for life to thrive. However, one of the main challenges in investigating the moon’s habitability is the nature of the concept itself. Nevertheless, the relevant parameters include hospitable temperatures, pressure, pH, salinity, and the presence of a solvent (such as water).
Steven D. Vance, the Deputy Section Manager for the Planetary Interiors and Geophysics Group at NASA’s Jet Propulsion Laboratory (JPL), was also the paper’s lead author. As he explained to Universe Today via email:
“Habitability is the potential for supporting life, but not necessarily the presence of life. Some environments are more habitable than others. For example, a lush rainforest provides
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NASA’s Interstellar Mapping Probe Prepares for a 2025 Launch
Engineers at NASA have completed an important milestone in developing the Interstellar Mapping and Acceleration Probe (IMAP) spacecraft. It’s now moving from development and design to the assembly, testing, and integration phase, targeting a launch in late Spring 2025. After launch, the spacecraft will fly to the Earth-Sun L1 Lagrange Point and analyze how the Sun’s solar wind interacts with charged particles originating from outside the Solar System.
IMAP will follow up on discoveries and insights from the two Voyager spacecraft and the Interstellar Boundary Explorer (IBEX) and will help investigate two of the most important overarching issues in heliophysics: the energization of charged particles from the Sun and the interaction of the solar wind at its boundary with interstellar space.
The mission will map the boundaries of the heliosphere — the electromagnetic bubble surrounding and protecting our solar system — and help researchers better understand the boundary of the heliosphere. This region is where the constant flow of particles from our Sun, called the solar wind, collides with material from the rest of the galaxy. This collision limits the amount of harmful cosmic radiation entering the heliosphere.
An updated model (left) suggests the shape of the Sun’s bubble of influence, the heliosphere, may be a deflated croissant shape, rather than the long-tailed comet shape suggested by other research (right). The white lines represent the solar magnetic field, while the red lines represent the interstellar magnetic field. Image Credits Opher, et al
It will also help settle the debate on the actual shape of the heliosphere. A study in 2020, using data from several spacecraft, suggested that the Sun’s bubble of influence may be a deflated croissant shape, rather than the long-tailed comet shape that has previously been
The spacecraft will be positioned about 1.5 million km (1 million miles) from Earth and will collect and analyze particles that make it through to help chart and understand the range of particles in interplanetary space.
The milestone the IMAP mission recently met is called Key Decision Point D, which allows the mission to move from development and design to the testing and integration phase. The targeted launch date was moved back one months, from late April to May 2025 to ensure that the project team has the adequate resources to “address risks and technical complexities during system integration and testing,” NASA said in a recent mission blog post.
The spacecraft is currently being assembled inside the clean room at the Johns Hopkins Applied Physics Lab in Laurel, Maryland. There is a live, 24-hour feed where you can watch the assembly, integration, and testing.
During the next few months, engineers will install the electronics, communications systems, thermal systems, propulsion, batteries, and many more complex systems to make the spacecraft work. Additionally, all 10 of IMAP’s instruments will soon start to arrive from around the world and be integrated with the spacecraft one by one. Finally, the spacecraft will begin testing before being sent to NASA’s Goddard Space Flight Center for final testing prior to launch.
Learn more about the mission and the huge team of universities and organizations that are part of IMAP at the mission website.
The post NASA’s Interstellar Mapping Probe Prepares for a 2025 Launch appeared first on Universe Today.
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Does Betelgeuse Even Rotate? Maybe Not
Betelgeuse is the well known red giant star in the corner of Orion the hunter. The name translated in some languages means ‘armpit of the giant’ which I think of all the star names, is simply the best! Betelgeuse has been fascinating observers of late not only because it unexpectedly faded a few years ago but more recently a study shows it’s super fast rotational speed which is, when compared to other supergiants, is like nothing seen before.
One of the brightest stars in the northern hemisphere sky, in fact the tenth brightest, Betelgeuse has a stunning red colour. It is a semi regular variable star which means there is some regularity to its varied light output but there are occasions, perhaps lasting between 20 and 2000 days where the variation is interrupted. If Betelgeuse were placed in the Sun’s position then its visible surface would more than likely extend beyond the orbit of Mars and swallow up everything in between.
1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles (Credit : STScI, NASA, ESA)
Like all stars, Betelgeuse rotates but a recent study using the Atacama Large Milimeter Array (ALMA) has showed that Betelgeuse is rotating faster than expected. Cool stars like Betelgeuse expand as they evolve and to conserve momentum the rotation must slow. It is possible that mass loss due to stellar winds decreases rotation speeds further. The current theory predicts that red giants rotate at around 1km per second while red supergiants a little less than 0.1km per second.
Two of the Atacama Large Millimeter/submillimeter Array (ALMA) 12-metre antennas (Credit : Iztok Bon?ina/ESO)
Current theory aside it seems there have been a number of observations of at least a few hundred giant stars rotating faster. Betelgeuse in particular has shown faster than expected rotation. Somewhat usefully, it’s proximity to Earth has meant its surface can be resolved and accurate measurements taken. Measurements showed that half of the visible hemisphere was blue shifted and the the other half red shifted. We can use this information to accurately calculate a rotational velocity.
When it comes to Betelgeuse, the radial velocity with ALMA was measured to be around 5.47 km per second. This value was compared against previous observations using Hubble Space Telescope and thankfully this agreed. One leading theory takes binary star evolution as a possible cause and in particular a merger with a low mass companion star. This is not an unusual process with an expected one-third of red supergiants experience stellar merger before their core collapses marking the end of their life. When it comes to red giants the team considered the impact of merging with planetary systems on the rotational velocity.
There are complications however in attaining sufficient data but the team modelled 3D radiation hydrodynamic simulations of red supergiants with properties similar to Betelgeuse. Throwing a proverbial spanner in the works, the team suggest that it is possible that the observations could be wrong and false signals have been picked up from churning convective plasma at the surface rather than the rotation of the star itself!
In an attempt to ascertain if it is possible to accurately measure the rotational speed of red giants and supergiants they had to develop new processing techniques to establish predictions that they could compare with observations of Betelgeuse. The team finally conclude that to be able to establish without doubt that Betelgeuse and other red supergiants are rotating
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