New books about life in our galaxy, and beyond it.

Some years ago, when I lived in Providence, I learned to avoid a busy intersection where five streets converged. A friend’s cousin had dubbed this spot “Death by Five Choices,” and it was apt. Eventually, a traffic light was installed, but even then, you took your chances.

Katie Mack, an astrophysicist, might observe that such earthly concerns are minor. With “The End of Everything (Astrophysically Speaking),” she brings word that the universe itself faces a five-way finale. No escape from one of these possible extinctions is currently foreseen.

If this sounds depressing, in Mack’s hands it oddly isn’t. She is as upbeat as she is fluent in her subject, the kind of endearing geek who will gleefully correct scientific inaccuracies in a “Star Trek” episode. You do not really need to know the math, she avers, to appreciate some of the most suggestive ideas in contemporary physics.

Lest readers toss her book prematurely, Mack cheerfully notes that (with one possible exception) humanity will not be around to witness the end. Earthly existence will cease first, about 5 billion years from now, when a swelling sun chars the planet to a crisp.

After that? Death by five choices.

Probably the easiest possibility to grasp is what Mack calls the Big Crunch. Under this theory, the expanding universe will reverse course and collapse on itself. Trickier to comprehend is vacuum decay (the previously-noted exception). In this scenario, a tiny vacuum bubble forms somewhere in the cosmos, setting off an annihilating cascade of destruction. Vacuum decay is highly unlikely — but in theory it could happen at any moment.

Throughout this lively and lucid account, Mack evinces a boundless faith in her readers’ capacity to follow along. Dry theory is leavened with the kind of examples that must make her a popular professor (currently, at North Carolina State). My favorite: under a principle of statistical mechanics, if you wait long enough, an entire piano can reassemble itself inside a box.

Never mind the implications, Mack advises at every turn; this stuff is just cool.

For other scientists, what’s cool begins with what is actually visible. In “The Last Stargazers — the Enduring Story of Astronomy’s Vanishing Explorers,” Emily Levesque describes her path from a backyard telescope in Taunton to research work at observatories around the world.

Levesque is exhilarated by the technological advances that have occurred in her field. However, with data collection now much easier, she fears that the adventure stories of earlier astronomers may become lost. “The Last Stargazers” shares some of this history, taking readers to remote locations where exhausted researchers had to sit beside cameras at 3 a.m., tending glass plates and keeping themselves warm in heated flight suits. Today’s astronomers can observe the stars from temperature-controlled rooms.

Like Levesque, Sara Seager found herself captivated by the heavens as a girl. In “The Smallest Lights in the Universe,” she recalls being bowled over by the stars during a camping trip when she was 10.

After a sad childhood, Seager seemed headed for a charmed life. Her studies in astrophysics took her from Harvard to the Institute for Advanced Study and a MacArthur fellowship. Offered a tenured position at MIT at age 36, she worried that she might be settling. At home (a yellow Victorian in bucolic Concord), a saintly husband, Mike, managed domestic affairs and their two young sons.

Seager’s memoir is half hymn to the stars and half guide to grief recovery. Mike’s slow death from cancer left her an overwhelmed single mother at 40. Though socially awkward, she joined a widow’s group. She took on the household tasks Mike had outlined for her in writing and in one moment of everyday crisis, taught herself how to disconnect a light fixture.

Meanwhile, lured by her faith in finding life elsewhere, she continued her research on exoplanets — versions of other star-orbiting Earths — and methods for detecting them.

Long before exoplanets were discovered, Mars was seen as the best bet for finding company beyond ourselves. In “The Sirens of Mars: Searching for Life on Another World,” planetary scientist Sarah Stewart Johnson offers an absorbing chronicle of researchers’ waxing and waning hopes. (Lately, with the landing of Perseverance, they wax.)

Her captivating account of the world’s first mission to Mars — Mariner 4, in 1965 — ends with a crushed President Johnson reviewing the desolate photographs sent back, and positing that we may be alone after all.

Since then, more sophisticated technology has continually revised scientists’ assumptions. In 2008, ice was found on Mars. In 2016, an analysis performed by the Curiosity rover detected all six elements thought necessary for life.

Together, these books suggest there could be no better time for pondering the secrets of the universe. In fact, why wait? Sourcebooks, Emily Levesque’s publisher, recently issued “Astrophysics for Babies.” An English major has to start somewhere.

M.J. Andersen is an author and journalist who writes frequently on the arts.