Supernova Remnants Expand Quickly

The remains of one of the few historically-observed
supernovas has expanded 5.5 times faster than expected

Our Milky Way has some 300 or more scattered supernova remnants that appear as beautiful nebulae. The Veil Nebula in Cygnus is well known. Astronomers have been puzzled by the paucity of predicted supernova remnants in the Milky Way: five times fewer than expected. Astrophysicist Paul Sutter tried to explain why at Universe Today on 6 Jan 2021. This year, Andrew Hopkins (The Conversation, 20 Jan 2023) reported more “possible” remnants found in the most detailed radio images—3 times as many in one segment—which may fill in the gaps.

Expansion Timing

A NASA article on supernova remnants (March 2011) explained how astronomers estimate the age of a supernova remnant by its dimensions, radius and speed. Only a handful of supernova explosions, though, have been recorded by human observers (see list of 7 from Astronomy Magazine). These include SN 1987A, Tycho’s Star (1572), Kepler’s star (1604), the Crab Nebula (1054) and a few others. Only these allow actual measurements of expansion speed of their remnants. The most interesting (and oldest) is the “guest star” observed by Chinese astronomers in 185 A.D (hence SN 185). That occurred 1,837 years ago. New findings show that the SN 185 remnant has expanded much faster than theory predicted.

The National Science Foundation, via Phys.org, reported 1 March 2023 new measurements of the expansion speed of RCW 86, thought to be the remnant of SN 185.

This historical supernova, which astronomers now refer to as SN 185, occurred more than 8000 light-years away in the approximate direction of Alpha Centauri, between the constellations of Circinus and Centaurus. The resulting structure, RCW 86—as imaged by the Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF’s NOIRLab—helps shed light on how the remains of the supernova evolved over the past 1800 years. DECam’s amazing wide-field vision enabled astronomers to create this rare view of the entire supernova remnant as it is seen today.

Puzzle Solved

Astronomers had been uncertain about the association of observed remnant RCW 86 and the Chinese “guest star” – why?

Though the link between RCW 86 and SN 185 is now well established, that wasn’t always the case. For decades, astronomers thought it would take about 10,000 years for a traditional core-collapse supernova—one in which a massive star blows material away from itself by exploding—to form the structure as we see it today. This would make the structure far older than the supernova observed in the year 185.

How could an 1837-year-old supernova create a 10,000-year-old structure? That’s 5.5 times the expected expansion rate! This calls for questioning assumptions.

This preliminary estimate largely came from measurements of the supernova remnant’s size. But, a 2006 study found that the large size was due instead to an extremely high expansion velocity. The new estimate is much more in line with a comparatively youthful age of about 2000 years, which strengthened the link between RCW 86 and the guest star observed centuries ago.

We reported the 2006 study here at CEH on 1 Oct 2006. And so now, 17 years later, astronomers are facing the hard fact that astronomical objects can surprise experts.

Theory Rescue

How are astronomers explaining their mistake? The article goes on to say, ‘Oh, we didn’t realize this was a Type Ia supernova. Those expand faster than other supernovas.’ Whether or not the explanation satisfactorily accounts for a 5.5-fold increase in expansion rate is beyond the scope of this article.

Measuring the distances to supernova remnants and determining the type of supernova are not always straightforward (see “Supernova Dating and Classification Is Not Simple,” 30 Sept 2012). Additionally, it is very difficult to infer what obstacles or conditions may have accelerated or decelerated a particular supernova’s expansion. Estimates become less empirical and more theory laden. When astronomers make confident statements about processes requiring far more time than the Biblical timeline allows, therefore, we can suggest waiting for a few years for the science to catch up.

Creation astronomers have noted the lack of supernova remnants as evidence for a younger universe (Sarfati, 2011). Danny Faulkner (PhD, astronomy), however, advised against using that argument (Faulkner, 2017), finding flaws in a 1994 ICC paper about it and believing that some of the older supernova remnant age estimates were not properly considered. For me, having observed theories crash and burn with new evidence, I continue to recommend maintaining a healthy skepticism about the certainty of expert claims (Coppedge, 2007), given their track record of being 80% wrong or more.

Consider, for instance, if you had been told in 1999 the consensus belief that the Veil Nebula was tens of thousands of years old. Suppose that caused you to doubt the Biblical timeline and started you questioning your faith. Suppose you never heard about the 2001 correction that shorted its age to only 5,000 years old; the damage would have been done. What can we learn from this? On one hand, inaccurate arguments in support of the Bible need to be corrected, as Faulkner has done. But on the other hand, unwarranted trust in the secular scientific consensus has been a doorway to apostasy (example: 12 Jan 2007). A healthy philosophy of science neither discounts empirical rigor nor places unearned trust in fallible human thought. The Bible teaches a robust scientific attitude: “Prove all things; hold fast that which is good” (I Thessalonians 5:21).